Polymerizable polyester compositions



United States Patent 3,268,621 PGLYMERKZABLE POLYESTER COMPUSITIUNSRichard N. Moore, El Dorado, Ark, and Ray V. Lawrence and Walter H.Schuller, Lake City, Fla, assignors to the United tates of America asrepresented by the Secretary of Agriculture No Drawing. Originalapplication July 3, 1961, Ser. No. 131,703. Divided and this applicationOct. 24, 1962, Ser. No. 239,390

1 Claim. (Cl. 260-861) A non-exclusive, irrevocable, royalty-freelicense in the invention herein described, for all governmentalpurposes, throughout the world, with the power to grant sublicenses forsuch purposes, is hereby granted to the Government of the United Statesof America.

This application is a division of Serial No. 131,703, filed July 3,1961, now U.S. Patent No. 3,230,235, which is a c-ontinuation-in-part ofSerial No. 653,255, filed April 16, 1957, now U.S. Patent No. 2,996,515.

The invention which is the subject of this application relates to theuse of the novel peroxides of Serial No. 131,703 as polymerizationcatalysts.

The process of this invention is carried out by passing an excess of anoxygen containing gas through the rosin acid or neutralized rosin acidto which a sensitizing organic dye has been added, while illuminatingthe mixture with artificial light (incandescent or fluorescent) orsunlight.

Products produced by the direct, non-photochemically induced oxygen orair oxidation of the rosin acids are dark colored heterogeneous mixturesformed in low yield. No more than about ten mole percent concentrationof rosin acid peroxide can be prepared by processes other thanphotochemically induced oxidation since at this concentration the rateof decomposition of the peroxide equals the rate of peroxide formation.

In accordance with this invention, carboxylic acids such as abieticacid, neoabietic acid, levopimaric acid, palustric acid, and thederivatives of these acids such as the esters and the salts, can bephotochemically oxidized to produce, in high yield, compounds thatcontain active oxygen (peroxides).

The photochemical oxidation reaction of this invention is applicable toconjugated dienic rosin acids, the esters of conjugated dienic rosinacids, and the salts of conjugated dienic rosin acids. Moreover, sincethe carboxyl group does not enter into the oxidation reaction or ailectthe oxidation reaction in any way except to the extent that the abilityof the carboxyl grouping to form soluble derivatives can influence thechoice of the solvent to be employed, when use of a solvent is dictatedby the physical characteristics of the starting material (i.e. startingmaterial a solid at the temperature selected for the photochemicaloxidation reaction), the process of this invention is applicable to anycompound that contains a reactive conjugated diene grouping.Neoabietinol, levopimarinol or the corresponding hydrocarbon compounds,for ex ample, can be photochemically oxidized with equivalent results bythis process.

Satisfactory solvents for use in the practice of this invention, whereuse of a solvent is indicated, are Water, alcohols, ketones or any polaror semi-polar solvent for the conjugated dienic material being subjectedto photochemical oxidation.

When use of a solvent is indicated for the photochemical oxidationprocess of this invention, the solvent in addition to possessing goodsolvent power for the conjugated iiihdfizl Patented August 23, i966dienic material, must transmit the active wavelengths of light which arefrom about 2000 to 7000 A. and be inert toward the conjugated dienicmaterial and the active oxygen compounds produced by the process.

The temperature at which the photochemical oxidation process of thisinvention is to be carried out can be room temperature (20-30 C.) aboveor below, e..g. 1045 C. The operational temperature of the process islargely a matter of convenience. Photochemical oxidation processes areaccelerated only to a slight degree by an increase in temperature.However, high temperatures should be avoided to prevent undesirable sideand secondary reactions which are accelerated by increases intemperature.

Temperatures higher than room temperature can be employed foroperational convenience if the pH of the reaction is kept at or near topH 7, but as indicated above, the yield of active oxygen product will beless at the higher temperatures due to side and secondary reactions.

The pH at which the photochemical oxidation is best carried out is pH 7or below since the oxidation reaction is more rapid at lower pH andfurthermore secondary reactions are induced by an excess of alkali. Thestability of the conjugated dienic material undergoing photochemicaloxidation must, of course, be considered when choosing the optimum pHfor a particular reaction. In the case of levopimaric acid, excessiveamounts of mineral acid are not desirable because isomerizationreactions may be induced. Also, as shown in Example 7 below, thephotochemical oxidation of the alkali metal salts of levopimaric acid inthe presence of an excess of alkali leads to a base catalyzedrearrangement of the peroxide salt, as described in our co-application.

The rate of oxidation is basically limited by the intensity andcharacteristics of the light source, and is independent of theconcentration of the rosin acids over a wide range of concentration. Noincrease in oxidation rate is obtained by employing very high rosin acidconcentrations, but side reactions become competitive with the oxidationreaction and some reduction in yield of peroxides results. Dilutesolutions will therefore be commonly employed in the practice of thisinvention. Low rosin acid concentrations may be maintained by additionof the rosin acids at a suitable rate to the solution as the reactionprogresses, so that the final product is quite concentrated with respectto peroxides.

Any gas that contains free oxygen and is of itself inert under theconditions of the photochemical oxidation reaction can be used to carryout the process of this invention. It is essential that an excess ofoxygen be kept dissolved in the reaction mixture during thephotochemical oxidation process in order to prevent undesirable sidereactions such as photochemical isomerization, the latter brought aboutby a deficiency of oxygen during the process operation. Any efiicientmethod of agitation such as stirring or bubbling the oxygen containinggas through the reaction mixture can be used to maintain an excess ofoxygen gas dissolved in the reaction mixture. Because it is desirable tomaintain an excess of oxygen in the reaction mixture there is someadvantage in the use of pure oxygen and in the use of pressures greaterthan atmospheric for carrying out this reaction.

The choice of the material to be used as a photo-sensitizer for thephotochemical oxidation reaction depends in large measure on the otherreaction variables, the spectral characteristics and intensity of thelight being used, the light transmission characteristics of the reactionmixture and the reaction container and the quantum efficiency of thephotosensitizer.

The choice of concentration of the photosensitizer is dictated by thesame variables plus its own transmittancy of active light wavelengthsand the dimensions of the reaction vessel. The concentration of thephotosensitizer can be adjusted along with the other variables toachieve the most economical compromise between the use of light and ofphotosensitizer material. The following photosensitizers have been foundto function satisfactorily under the conditions described: rose bengal,methylene blue, erythrosin, eosin, retene quinone, 1,2-naphthoqui none,chlorophyll, and fiuorescein.

The photosensitized oxidation of heteroannular conjugated dienes hasbeen previously reported to be specifically limited to cisoid dienes [D.H. R. Barton and G. F. Laws, J. Chem. Soc., 52 (1954)]. The presentwork, especially the photosensitized oxidation of neoabietic acid andabietic acid, constitutes the first demonstration of thephotosensitizezd oxidation of a transoid conjugated diene. [See W. H.Schuller and I. V. Lawrence, Chemistry & Industry, 105-106 (1961)]. Thisis a new finding of considerable scope, utility, and importance. Thestructure of the product from the photosensitized oxidation ofneoabietic acid and abietic acid could not have been predicted from aknowledge of all the prior literature and the results obtained from thisreaction were entirely unexpected. The structure of the diperoxide fromneoabietic acid, for example, clearly is an exception to the teachingheld until this time (e.g. see Tobolsky et al.) that a parallelismalways exists between the structure of the maleic anhydride adduct andthe structure of the peroxide formed on photosensitized oxidation. Thereaction of all four resin acids (levopimaric, neoabietic, palustric,and abietic) with maleic anhydride yields the same product, namely,maleopimaric acid, which is a 6,14-adduct of maleic anhydride. Thestructure of neoabietic acid diperoxide, abietic acid diperoxide, andpalustic peroxide as described herein, clearly demonstrate that noparallelism exists in these cases, between the addition of maleicanhydride and the photosensitized addition of oxygen.

The new compound, neoabietic acid diperoxide (18-hydroperoxy-6,l4-peroxy-A -dihydroabietic acid) has been found useful inconjunction with certain accelerators, in the room temperature curing ofpolymer systems such as the sytrenated polyester type laminating resinscommonly employed in the manufacture of boats and so forth. The compoundis also useful in the two stage curing of certain polymer systems (e.g.casting resins) as the two peroxide groups decompose thermally atdifierent temperatures.

The compound from the bisulfite reduction of the hydroperoxy group to ahydroxy group in neodiperoxide (18-hydroxy-6,14-peroxy-A -dihydroabieticacid) is also useful as an initiator for the polymerization of vinylmonomers as are levopimaric acid transannular peroxide, palustric acidtransannular peroxide, the crude peroxide mixture from thephotosensitized oxidation of gum rosin, the crude peroxide from thephotosensitized oxidation of pine gum, and the product(18-hydroperoxy-6-keto-14- hydroxy-A -di hydroabietic acid) obtained 'bythe treatment of neoabietic acid diperoxide with base.

The following examples illustrate the process of photochemicallyoxidizing carboxylic acids and derivatives of carboxylic acids thatcontain a conjugated dienic grouping to produce active oxygen compounds.

EXAMPLE 1 A cylindrical pyrex vessel containing 15.1 g. of devopimaricacid, 2.0 g. of sodium hydroxide, 0.0225 g. of eosin, and sufficient 95%alcohol to produce 450 ml. Of solution was irradiated by a wattfluorescent lamp while a stream of oxygen was passed through thesolution at a rate suflicient to keep the solution saturated with re- 4spect to oxygen. The optical rotation of the solution changed from [0:1276 to [111 +67 in 42 hours based on the original concentration ofdevopimaric acid.

The peroxide was isolated essentially free of the sensitizer and in ahigh state of purity by removing most of the alcohol by vacuumdistillation, and treating the pot residue with 200 ml. of acetone, andfiltering out the precipitated sodium salt of the peroxide. The recoveryof the purified salt of the peroxide was 11.60 g. or of the theoreticalyield. The salt was dissolved in a little alcohol and acidified withdilute acetic acid. The free rosin acid peroxide crystallized when thealcohol was diluted with a little water. After recrystallization oncefrom aqueous alcohol the peroxide melted at 152-154 C. and weighed 7.43g. The numbering in the structural formula is according to Sirnonsen,The Terpenes, vol. III, page 374 (second edition, at University Press,Cambridge, Eng land).

EXAMPLE 2 A crude sample of levopimaric acid photoperoxide obtainedunder oxidation conditions similar to those described under Example 1,was purified by precipitation from alcohol solution with2-amino-2-methyl-1-propanol. The precipitate was white after tworecrystallizations from ethanol and had a specific optical rotation of-+77.1 (1% in ethanol). The amine addition compound was slurried inether and acidified with dilute acetic acid. The ether layer wasseparated, Washed several times with water, dried over anhydrous sodiumsulfate and filtered. The ether was .then evaporated from the filtrateand the residue was recrystallized once from alcohol-water. The peroxidepurified in this manner melted at 158l59 C., had a neutral equivalent of334 and a specific optical rotation of +101 (1% in alcohol). Analysisfor carbon and hydrogen content Was in good agreement with thecalculated values for an intramolecular peroxide of formula C H O Theperoxide when treated with methyl magnesium iodide, liberated 1 mole ofmethane per neutral equivalent and therefore contained no activehydrogen other than the one present in the carboxyl group.

EXAMPLE 3 A sample of levopimaric acid photoperoxide from Example 2 wasdissolved in ether and treated with a slight excess of diazomethane. Themethyl ester of the peroxide readily crystallized after removal of thesolvent under vacuum, and melted at 100-101 C. after recrystallizationfrom aqueous alcohol. It had [001D +93.5 (2% in alcohol) and its carbonand hydrogen content was found by analysis to be in good agreement withan empirical formula of C H O The infrared absorption spectrum of themethyl ester showed no charactery istic OH stretching band in the regionof 3 microns.

EXAMPLE 4 A solution containing 0.604 g. of methyl levopimarate ([ah270, i i- 272 millimicrons a 18) no characteristic absorption between220 and 320 millimicrons. The alcoholic product solution was dilutedWith a large volume of water and extracted with ether. The ether extractwas dried over anhydrous sodium sulfate, filtered and the ether wasremoved by distillation. The residue (0.62 g.) melted at 9698 C. aftertwo recrystallizations from alcohol-water. The melting point was notdepressed when the ester was admixed with an equal amount of the esterobtained under Example 3.

EXAMPLE 5 A solution containing containing 28.0 g. of levopimaric acidand 0.28 g. eosin in 2.8 liters of 95% ethanol was changed to anoxidation vessel consisting of concentric tubes, the outer tube being7.5 by 125 cm. with a. sintered glass bottom, and the inner tube being4.5 by 130 cm. and containing a 40 watt fluorescent lamp. A vigorousstream of air bubbles was passed through the alcoholic solution and thefluorescent light was turned on. After two hours the ultravioletspectrum showed that only 34% of the levopimaric acid remainedunoxidized. This amounts to a conversion of 231 g. of levopimaric acidper kilowatt hour of power.

EXAMPLE 6 In order to study the variables affecting the photochemicaloxidation of the abietic type resin acids, a set of four cylindricalPyrex test tubes of 2.8 cm, outside diameter and 25 cm. long wasobtained. The tubes were fitted with reflux condensers and a sinteredglass pencil type gas inlet near the bottom of each tube. Each tube wasmasked with opaque paper so that only a cylindrical center section 140mm. long was exposed to light. Photochemical oxidation in quadruplicate,of alcoholic solutions of 0.02 molar levopimaric acid sensitized by 50mg. of eosin per liter gave a maximum diiTerent in observed opticalrotation of 007 during the reaction. When no sensitizer was employed,the optical rotation of the levopimaric acid remained unchanged during14 hours of irradiation and aeration. When the concentration of eosinwas increased from 50 mg. per liter to 100 mg. per liter, the rate ofchange in [u] was increased from 52.2 per hour to 59.4 per hour.

EXAMPLE 7 Four 100 ml. solutions in 95% ethanol each containing 0.002mole of levopimaric acid and 5 mg. of eosin and containing also in (1)0.000 mole of NaOH, in (2) 0.001 mole of NaOH, in (3) 0.002 mole ofNaOH, and in (4) 0.003 mole of NaOH, were prepared and placed in thefour test tubes described under Example 6. The tubes were irradiated bya 15 watt fluorescent lamp while a stream of gaseous 0 was bubbledthrough. The changes in the optical rotations of the first three tubesshowed that the reaction was not altered by addition of up to 1equivalent of NaOH per equivalent of levopimaric acid. The reaction intube (4) was altered by the presence of excess NaOH, as furtherdescribed in U.S. Patent Number 2,899,463.

EXAMPLE 8 A number of oxidati-ons were conducted using 100 ml. ofsolution in 95% ethanol containing 0.002 mole of levopimaric acid andvarious sensitizers. The reactions were conducted in the tubes describedin Example 6 and a 15 watt fluorescent lamp was employed as a lightsource. The oxidation was found to be sensitized by rose bengal,methylene blue, erythrosin, eosin, retene quinone, 1,2- naphthoquinone,alcohol soluble chlorophyll and fluorepcein. No reaction occured in theabsence of sensitizer.

EXAMPLE 9 A solution of 8.16 g. of neoabietic acid and 0.135 g. oferythrosin B (0.01 M in resin acid and 50 mg./l. in dye) in 2700 ml. of95% ethanol was charged to the reactor described in Example 5 above. Thereaction Was followed by the change in [111 and was well over in 2 hr.(no change in specific rotation on further aeration and irradiation).The solution was stripped under reduced pressure to about 100 ml.,chilled in an ice bath, and 3.35 ml. of freshly distilledcyclohexylamine added slowly with stirring and cooling; final pH 9. Onstanding, the crystalline salt slowly appeared. It was collected byfiltration, washed thoroughly with pentane and dried over Drierite,yield 8.64 g. (69%). The salt was dissolved in 95% ethanol (containing afew drops of cyclohexylamine) at about 50 to 60 and on cooling a firstcrop, 2.83 g. and a second crop, 2.33 g. were obtained, both of the samerotation; [(11 +72.2 (c.=0.476), rotation unchanged on furtherrecrystallization. The pure salt exhibited M.P. 181181.5 with dec. andevolution of gas; no characteristic absorption from 220320 III/L; )t(Nujol m-ull) 2.95 4 (s), 6.20 t (s), 8.78 (s), no band in 5.8a region.

Analysis.-Calcd. for C H NO C, 67.1; H, 9.3; N, 3.0; neut, equiv., 466.Found: C, 67.3, 67.3; H, 9.4, 9.4; N, 3.0, 3.0; neut. equiv., 467.

The cyclohexylamine salt of18-hydroperoxy-6,l4-peroxy-A7(8)-dihydroabietic acid (2.55 g.) wassuspended in ether and shaken with dilute aqueous phosphoric acid (1mole phosphoric acid/ 1 mole salt). The other layer required only twowater washings to be free of mineral acid. Evaporation of the ether gave2.03 g. of the free acid which was crystallized from aqueous methanol,yield 1.77 g. of needles; [111 +9l.7 (c.=1.0). Recrystallization fromaqueous methanol gave star clusters, yield 0.67 g.; [u] +94.4(c.=l.08),. rotation unchanged on further recrystallization; M.P. 176 C.with dec. and evolution of gas; no characteristic absorption from220-320 m A (Nujol mull) 302 (s), 5.92 7 (5), 8.81,LL(S), no bands inthe 6.05 region and no strong bands in the 11 to 12 region; k (CHCl 285(s), 5.92,u(s).

Analysis.-Calcd. for C H O C, 65.6; H, 8.3; neut. equiv., 366. Found: C.65.6, 65.6; H, 8.5, 8.6; neut. equiv., 368.

PEROXIDE ANALYSES E OF RELATED COMPOUNDS FOR VARYING REACTION PERIODSWITH REAGENT b 18-Hydroperoxy-6,14-peroxy-A )-dihydroabietic acid.

Cyclohexylamine salt of l8-hydroperoxy-6,l4-peroxy-A )-dihydr0- abietieacid.

11 6,14-Peroxy-A G)-dihydroabietic acid.

0 The results for N eOP and LAP were plotted as a function of time andthe values taken from the plots used in calculating the difference,NeOP-LAP.

Methyl 18-hydroperoxy-6, l4-peroxy-A -dihydrobiate was (prepared usingdiazomethane in ether solution. The residue, after solvent stripping,was crystallized from methanol-water; yield 0.48 g. (81%); [M +91.3(c.=0.489). Recrystallization from methanol-water gave long needles;yield 0.33 g.; +91.3 (c.=0.936), M.P. 147l47.5 with dec. and evolutionof gas; no characteristic absorption from 220320 m peroxide analysis(peroxide analysis via the modified Wheeler method, 1.0 hr. reactionperiod in the dark) 1.79 moles peroxide/ mole of ester; A (Nujol mull)2.97 7 (s), 5.81 (s); k (CCI 2.83 (W), 2.93 (m), 5.79 (s).

Analysis.Calcd. fOT 02111320 C, H, 3.5. Found: C, 66.6, 66.6; H, 8.6,8.5.

A comparison of the nuclear magnetic resonance spectra of the methylesters of 18-hydroperoxy-6,14-peroxy-A' dihydroabietic acid and6,14-peroxy-A -dihydroabietic A acid confirms the structure of theformer compound to be as indicated. The liberation of acetone on thetreatment of 18-hydroperoxy-6,14-peroxy-A -dihydroabietic acid with baseand the-n with strong acid confirms the location of the hydroperoxidegroup on 018 (see reference cited above). Again, the similarity of molarrotations of 18- hydnoperoxy-6,14-peroxy-A' -dihydroabietic acid (M+346) and 6,14-peroxy-A' -dihydroabietic acid (M +338) confirms thestructure of the former compound to be as indicated as the nonasymmetryof the C-18 carbon atom would result in little change in M onreplacement of the C-18 hydrogen with another group such as -OOH.

EXAMPLE 10 To 0.50 g. of 18-hydroperoxy-6,14-peroxy-A -dihydroabieticacid was added 2.08 ml. of 0.916 N sodium hydroxide (1.4/1base/diperoxide) and diluted to 25.0 ml. with water. The specificrotation dropped rapidly from +94 to +21 in 24 min. with little furtherchange to 75 min., at which time 0.64 ml. of 0.52 N acetic acid wasadded; final pH 5. A precipitate came down, yield, 0.25 g. (52%); [a]+4l.9 (c.:0.989); A 234 mu, =93; peroxide content 0.54 moleperoxide/mole of hydroxy-ketone; A 2.95,u (s), 5.9a (s), 6.04 (s). Thishydroperoxide has the structural formula G OH O OOH EXAMPLE 1 l EXAMPLE12 100 ml. of a solution containing 1.00 g, of commercial WW grade gumrosin and mg. of eosin in 95% ethanol was oxidized in the mannerdescribed in Example 6. Analysis of the solution after 24 hours reactionshowed it to contain at least 2.06 milliequivalents of active oxygen.Assuming the average molecular weight of rosin to be 302, this wouldequal 0.62 atom of oxygen per molecule.

EXAMPLE 1 3 A solution of 0.604 g. of pure abietic acid in 100 ml. ofethanol containing 5 mg. of erythrosin B (0.02 M in resin acid and 50m-g./l. in dye) was charged to the equipment described in Example 4above and aerated and irradiated simultaneously. The reaction wasfollowed by the change in specific rotation, the increase in titratableperoxide, and the change in ultraviolet adsorption spectrum. After 45hr. irradiation and aeration, a peroxide analysis indicated the presenceof almost two equivalents of peroxide present per mole of resin acidcharged. The specific rotation fell during the reaction and leveled offfinally at [1x1 30. The absorption peak at 241 m characteristic ofabietic acid diminished steadily throughout the reaction and at the endof same, no characteristic absorption was observed from 220-320 mg. Thesolvent was stripped off under strongly reduced pressure and the abieticphotoperoxide dried in vacuo over Drierite; wt. 0.54 g.;

3.05;; (s) (OH absorption) strong end absorption below 220 m (R C=CR-H);neut. equiv. 374 (calc. for C H O +20 =368.4); reduction with an excessof bisulfite destroyed 48% of the peroxide content (ROOR is notreducible by bisulfite while bisulfite ROOH (excess) The methyl ester ofabietic acid photoperoxide was prepared in ether solution employing anexcess of diazomethane. This ester was molecularly distillated to givethe thermally rearranged product as indicated below.

ROI-I) CH3 0 O OH 0H3 COOCHs The thermally rearranged product, oralcohol, is characterized as follows: [06113 13 (c.=1% in 95% ethanol);high end absorption below 220 mp. (R C=CR H) 295p. (OH absorption)essentially no peroxide content.

- Elemental analyses: Found: C, 72.1; H, 9.1; (calcd. for CZQH3OOZ+OZZC, H, 9.3).

EXAMPLE 14 100 ml. of a solution containing mg. of eosin and 0.604 g. ofa mixture of resin acids comprised of 40% palustric acid, 40% abieticacid, 14% neoabietic acid and 7% non-conjugated acids in 95% ethanol wasoxidized in the manner described in Example 6. Analysis of the solutionafter 7.0 hours showed it to contain 1.51 milliequivalents of activeoxygen and no palustric acid.

EXAMPLE A reaction vessel was constructed of two concentric glass tubes,mounted vertically, the outer tube being 4.28 cm. in diameter and 54 cm.in length and fitted at the bottom with a sintered glass gas inlet andthe inner tube being 3.48 cm. in diameter and 55 cm. in length, sealedat its lower end and containing a commercial 15 watt fluorescent tubetype lamp. A solution comprised of 5.00 g. of palustric acid, 0.028 g.of rose bengal and sutficient 95% ethanol to give a total volume of 280ml. was charged to the intertubular space of the reaction vessel. Thesolution was sparged vigorously with alcohol saturated air andirradiated by the 15 watt lamp for two hours. The reaction temperaturewas in the range of 25 to 40 C. The destruction of the palustric acidchromophore is shown by the disappearance of the absorption maximum at awavelength of 266 millimicrons.

Reaction time, minutes: a at 266 ma 0 23.6 18.3

The peroxidic product was recovered by dilution of the alcoholicsolution with a large volume of water and extraction into ether. Theether was removed by vacuum distillation, and the peroxide was dissolvedin 5 0 ml. of acetone and precipitated as the 2-amino2-methyl-propanolsalt. Recrystallization of the salt three times from acetone gave 2.90g. of white needles. The peroxide was freed of the amine andcrystallized. A fraction of the crystalline peroxide, which melted withdecomposition at 116, showed 70 (2% in ethanol) gave a methy ester whichcould be purified by recrystallization from methanol. The purifiedmethyl ester showed 76 (2% in ethanol), melted at 125-4126 C., andliberated 1.2 equivalents of iodine per mole of sample in 1 hour inacidic potassium iodide solution. The peroxide was stable toward alkali,showed no selective ultraviolet absorption between 220 and i320millimicrons, contained no alcoholic hydroxyl group and was found byanalysis to have the composition C I-1 0 The peroxide was therefore theproduct of 1,4-addition of oxygen to the conjugated dienic grouping inpalustric acid, or 7,13-peroxy-A -dihydroabietic acid.

As in Example 1, above, the numbering in the formula is based onSimonsen, The Terpenes.

1 0 EXAMPLES 16 A solution comprised of 2.19 g. of levopimaric acid and2.0 ml. of tertiary-butyl alcohol was placed in a small glass tubefitted with a sintered glass oxygen inlet, and sparged with oxygen forseveral hours. The oxidate was taken up in a little ether and theoxidized resin acids were extracted by dilute aqueous sodium hydroxide.The alkaline extract was then acidified by acetic acid and the oxidatewas re-extracted into ether solution. Removal of the ether from theoxidate by vacuum distillation left a yellow glassy residue. The oxidatecontained 0.0114 atom of active oxygen per molecule of resin acid andits ultraviolet absorption spectrum showed maxima at the followingwavelengths (millimicrons) with the indicated specific extinctioncoefiicients (or) in ethanol solution: 236, or 10.1; 243, at 11.1; 252,a 9.2; 267, a 3. 8; 276, a 3.7. The nature of the absorption spectrumshows that the levopimaric acid was oxidized and isomerized to a complexmixture during air oxidation by the free radical autocatalyticmechanism. This illustrates the difference between ordinary autoxidationof rosin acids by the free radical autocatalytic process and thephoto-sensitized process of this invention.

While the foregoing examples have shown the photochemical oxidationreaction of this invention applied to the free acids, their methylesters and their sodium salts, any derivative of the acids in which thedouble bond structure is unchanged, can be oxidized. For instance theethyl, propyl, butyl or other alkyl esters or the aryl or aralkyl orhydroxy alkyl esters, or the esters with polyhydric alcohols such asglycerol or ethylene glycol can be oxidized with equivalent results.

EXAMPLE 17 A solution of 43.2 g. of commercial WW grade gum rosin in2700 ml. of 95% ethyl alcohol (about a 2% solution by weight) containing0.27 g. of methylene blue (100 mg./l.) was charged to the apparatusdescribed in Example 5 above. The solution was aerated and irradiatedsimultaneously for 14 hours at which point the ultraviolet absorption ofan aliquot of the reaction mixture indicated that the major part (aboutof the conjugated diene resin acids had reacted. The photosensitizedoxidation Was continued for 21 hours and 600 ml. of the reaction mixtureremoved, treated with activated charcoal, concentrated to "10 ml. underreduced pressure and a solid cyclohexylamine salt prepared by theaddition of 6.6 ml. of cyclohexylamine. This salt exhibited noabsorption in the 220-320 m region, was insoluble in acetone, water, petether, and benzene and soluble in hot alcohol. It gave a stronglypositive test for peroxides and initiated the polymerization of acrylicacid when warmed with same.

EXAMPLE 18 A second 600 ml. portion of the final reaction mixture fromExample 30 was concentrated to 100 ml. under reduced pressure, 4 g. ofsodium hydroxide added, and the alkaline solution refluxed for 15 min. Alarge excess of water was added and the oily base-rearranged ketonicproduct was separated, dissolved in acetone, and 8.0 ml. ofcyclohexylamine added. The white crystalline amine salt was collected byfiltration and dried; yield 4.13 g. It contained a ketone grouping asindicated by a positive chemical test for same and by the presence of aninfrared absorption band in the 5.81.1. and 235 my. regions. The saltwas insoluble in water and benzene and soluble in hot alcohol.

EXAMPLE 19 A solution comprised of 54 g. of WW grade commercial gumrosin and 0.135 g. of methylene blue was dissolved in sufficient ethanolto give a total volume of 1620 ml. (4% rosin by weight) and charged tothe large reactor described in example 5 above. Aeration and irradiationwere carried out simultaneously. Solution A was prepared by dissolving540 g. of WW gum rosin in 320 ml. of 95% ethanol. Solution A was addedcontinuously during the reaction at a rate of about 1 ml. per minute.The addition was discontinued after 520 ml. of Solution A had beenadded. Five hours after the last addition, the ultraviolet absorptionspectrum of an aliquot indicated that essentially all of the conjugateddiene resin acids had reacted with the exception of abietic acid whichhad reacted only to a rather low extent. Sixty hours of aeration andirradiation were carried out after the last addition of solution A. Theultraviolet absorption spectrum indicated that essentially all of theabietic acid present had reacted. The peroxide number was found to be1235. The solution was treated with fullers earth to remove the dye,concentrated to 400 ml. under reduced pressure, and the product thrownout of solution by the addition of an excess of water. The yield ofsolid was 276 g. It was in soluble in water, soluble in alcohol, and hada peroxide number of 726.

EXAMPLE 20 To a solution of 0.0732 g. of 18-hydroperoxy-6,14- peroxy-A-dihydroabietic acid in ml. of 95 ethanol was added 5 ml. of a 0.40 Msolution of potassium hydroxide in 95 ethanol (10/ 1 molar ratio ofhydroxide/ diperoxide). After standing overnight, 2 ml. of water wasadded followed by conc. hydrochloric acid to pH 1. The solution wasrefluxed 1.25 hr.; A 288 m a=9; no essential change in ultravioletspectrum on further refluxing for 0.75 hr. The reaction mixture wasvacuum stripped, the residue dissolved in water, extracted with ether,and the ether evaporated. The residue gave a positive phenol test, wasinsoluble in dilute acid, and water While soluble in alkali, ether, andalcohol. The infrared absorption spectrum exhibited maxima at thefollowing wave lengths: 2.95 3.45 5.655.73 (shoulder) ,w 5.90n, 6.15 7.1t, 7.27 t, and 7.95 The compound on heating in carbon tetrachlorideyielded an insoluble carbon-tetrachloride addition complex. The diphenolhas the following structural formula.

EXAMPLE 21 A solution comprised of 0.242 g. of neobietic acid and 2.0mg. of erythrosin B dissolved in 40 ml. of 95% ethanol (0.02 M in resinacid and 50 mg./l. in dye) was charged to a 50 ml. Erlenmeyer flaskfitted to a gas burette. The flask was immersed in a constanttemperature bath maintained at 26i0.3. The system was flushed and filledwith oxygen in the dark. Magnetic stirring and irradiation with a -Wattfluorescent lamp were started simultaneously and the reaction followedby means of periodic readings of the volume of oxygen absorbed. Oxygenabsorption was essentially complete in 3 hr. with no further oxygentake-up on 30 min. additional irradiation. The sample absorbed 34.8 ml.of oxygen at 260 and 760.8 mm. pressure which corresponds to 1.78 molesof oxygen per mole of neoabietic acid.

112 EXAMPLE 22 A number of dyes, quinones, and diketones were tested forphotosensitizing activity with the results as indicated in Table I.

TABLE I Testing of compounds as photosensitizers for the photosensitizedoxidation of resin acids GROUP A.COMPOUNDS OF RELATIVELY GROUPB-COMPOUNDS OF BORDERLINE ACTIVITY. m

h('l;1he percentage of neoabietic acid reacted is given in parenthesesafter t e ye.

1,2-naphthoquinonc n (5); basic iuchsin (5); thymol blue (4); martiusyellow (4); p-bcnzoquinone (3); acridine orange (3); fluorescein (2);biebrich scarlet (2); dimethylglyoxime (2); tartrazine (2); azorubin(1); bromphenol blue (1); benzopurpurin 4B (0); gallocyanin (0); crystalviolet (0); acid rosolic (0); benzil monoxime (0); 1,2-naphthoquinone-4-sulfonic acid, sodium salt (0); diacetyl (0); brilliant yellow (0);congo red (0) and auramine hydrochloride. (0).

The data for neoabietic acid are based on the decrease in a at 251 b Thedata for levopimarie and palustric acids are calculated from the overallreaction times reported in J. Am. Chem. Soc., 82, 1734 (1060). l

A 4% solution in oil obtained from the Keystone Chemurgica Corporation.

Eastman Kodak sublimed grade.

B In 3 hr., 54% reacted.

i Found, M.P. 125126; Lit. M.P. 125-126".

In 2 hr., 20% reacted.

h Found, M.P. 20720S.5; Lit., M.P. 206207.5.

i Solution bleached at 22 min., 0% reacted; 1.0 hr. 6% reacted; 2.0 hr.11% reacted.

3 Repeat experiment.

k Found, M.P. 95.5"; Lit., M.P.

1 At 22 min., 2% reacted; at 1.0 hr. 4% reacted; at 2.0 hr. 10% reacted.

m The purity of the last three compounds in Group A would indicate thatthe relatively low order of activity exhibited can probably be ascribedto the compound in question, while the activity of the compounds at thetop of the list in Group 13 might be due to the possible presence ofvery active impurities.

11 Eastman Kodak, practical grade, Lit., M.P. -120 dec.

EXAMPLE 23 The photosensitized oxidation of neoabietic acid was carriedout under essentially identical conditions in methanol, ethanol, and2-methyl-propanol-2 in the equipment described in Example 4 above. Theamount of resin acid reacted after 70 min. was calculated from thedecrease in a at 251 mg and found to be essentially identical in allcases.

4 Example 24 Photosensitized oxidations of neoabietic acid were carriedout in the equipment described in example 4 above, in which theerythrosin B concentration was varied. The reactions were followed bymeasuring at at 251 m periodically. The shape of the curve in all caseswas found to be the same. The rate at 500 mg./l. was about 10% greaterthan at 50 mg./l. while the rate at 50 mg./l. was about greater than at5.0 mg/L EXAMPLE 25 Employing the equipment described in Example 4 aboveand using .02 M solutions of levopimaric, palustric, abietic andneoabietic acids, respectively, in 95 ethanol, it was observed thatthere was no change in a at A 251 my,

nor of [a] after 6.0 hr. of each of the following treatments: aerationin the dark, irradiation with visible light, aeration plus irradiation,contact with erythrosin B in the dark, aeration plus erythrosin B in thedark, and irradiation plus erythrosin B. In the last experiment, the airwas first swept out of the ethanol solution with nitrogen and the systemsealed.

EXAMPLE 26 To a solution of 1.13 g. of 18-hydroxperoxy-6,14-peroxy-A-dihydroahietic acid in 20 ml. of chloroform was added 20 ml. of a 0.5 Naqueous sodium phosphate buffer to pH 6.0. Sodium metabisulfite (0.29g.; l/ 1 on a stoichiometric basis) was added with continuous stirringunder a nitrogen sweep. After 27 min. all the bisulfite had reacted,(aqueous layer did not bleach an iodine solution). Another 0.87 g. ofsodium metabisulfite was added (400% excess). The next day, the aqueouslayer rapidly bleached on iodine solution and the peroxide content ofthe chloroform layer was 0.77 mole peroxide/mole of18-hydroperoxy-6,14-peroxy-A' -dihydroabietic acid charged. The aqueouslayer was extracted with chloroform and with ether. The organic layerswere concentrated to 5 ml. Ether (15 ml.) was added and cyclohexylamine(0.36 ml.; 1/-) added dropwise. The precipitate was ether washed; yield1.05 g. (75%); [M +64.3 (c.=0.552). The salt was recrystallized from 95%ethanol-ether, [(1113 +67 (c.=0.433); no characteristic absorption from220-320 m X (Nujol mull) 2.87 (s), 6.14 (s), 8.93,LL(H1).

18-hydroxy-6,14peroxy-A' -dihydroalaietic acid was regenerated from thesalt (0.98 g.) with phosphoric acid. The yield of crude acid was 0.522g. (68% from salt), +82.3 (c.=0.32); after several recrystallizationsfrom aqueou-methanol, 0.10 g., [(11 +98.9 (c.=0.394; M.P., softened at156 and melted at 161.5 with dec.; peroxide content 0.89 moleperoxide/mole of 18 hydroxy 6,14-peroxy-A -dihydroabietic acid; x (Nujolmull) 2.90 (s), 5.88 4 (5), 882 (s); A (CHCl 275 (w), 2.81 (m), 2.87p.(m), 2.96 (m), 5.92 (s).

Analysis.-Calcd. for C H O C, 68.5; H. 8.6; neut. equiv. 350. Found: C,68.0; H, 8.9; neut. equiv. 351.

The above data plus the similarity of molar rotations of the18-hydroxy-6,14-peroxy-A' -dihydroabietic acid (M +347) thus preparedand the 18-hydroperoxy-6,14- peroxy-A -dihydroabietic acid (M +346)starting material show the structural formula of 18-hydroxy-6,l4-peroxy-A -dihydroabietic acid to be The methyl ester of18-hydroxy-6,14-peroxy-A -dihydroabietic acid was prepared employingdiazomethane in ether. After solvent stripping, the residue wasrecrystallized from diethyl ether-diamyl ether, yield 0.16 g. (59%); [M+96.2 (c.=0.266), no change in rotation on further recrystallizationfrom diethyl ether-dibutyl ether. Additional crops of ester raised thetotal yield to 78%. The pure ester, after drying at 78 and 0.01 mm.pressure over Drierite for 2 hr. exhibited M.P. 169.5- 171"; peroxideanalysis 0.66 mole peroxide/mole ester; no characteristic absorptionfrom 220-230 m x (Nujol mull) 2.88 4 (s), 5.82 (s).

A nalysis.CalCd. for C H O C, 69.2; H, 8.9. Found: C, 69.3; H, 9.1.

The ester could be sublimed onto a cold finger at about 160-165 and 0.01mm. without decomposition; sublimate M.P. 169.5-171.

Analysis.Found: C, 68.9; H, 8.8.

EXAMPLE 27 To a solution of 0.500 g. of l8-hydroperoxy-6,14-peroxy-A'dihydroabietic acid in 40 ml. of chloroform was added 40 ml. of a 0.5 Msodium phosphate aqueous buffer solution of pH 6.6. The 2 phase systemwas well stirred (magnetic stirrer) and a total of 0.195 g. of sodiumsulfite (50% excess) added in small portions. After 1.5 hours, thelayers were separated, the Water layer extracted with chloroform, thechloroform layers combined and 3.0 ml. of 0.92 N aqueous sodiumhydroxide added plus 2 ml. of water. The system was well shaken for 30minutes, the aqueous layer separated and 0.30 ml. of glasial acetic acidadded to the aqueous layer. A precipitate of 18-hydroxy-6-keto-14-hydroxy-A -dihydroabietic acid formed, yield 0.31 g. (72%after allowing for aliquots removed during the run); [(11 +307 (c.=0.52in 95% ethanol); A 234 mu (06:8.8), A (Nujol rnull) 2.98 1 (5), 5.9 (s);6.05 a shoulder. The structural formula of this compound is for:

OOOH

Further evidence for the correctness of this structure is found in theChem. & Ind. (London) reference cited in Example 9 above.

EXAMPLE 28 A solution of 0.288 g. of neoabietinol [for preparation 7 ofsame see V. M. Loeblich and R. V. Lawrence, J. Am. Chem. Soc., 79, 1497(1957)] and 5 mg. of erythrosin B in 100 ml. of ethanol was charged tothe: reactor described in Example 4 above and irradiation and aerationwas carried out simultaneously for 5 hours after which no further changein specific rotation was noted. The solvent was stripped off underreduced pressure and the residue crude diperoxide was recrystallizedfrom aqueous ethanol. The alcohol peroxide exhibited a peroxide contentof 1.5 moles peroxide/mole of 18-hydroperoxy- 6,14-peroxy-A-dihydroabietinol; it exhibited no characteristic absorption in the220-320 m range; +98 (c.=1.0 in ethanol); exhibited a very strong OHband at 2.88 had a neutral equivalent of zero; and initiated thepolymerization of styrene on warming with same. The structural formulaof this diperoxide is EXAMPLE 29 A solution of 0.316 g. of methylneoabietate and 5 mg. of rose bengal in 100 ml. of 95% ethyl alcohol wascharged to the apparatus described in Example 4 above and was irradiatedand aerated for five hours after which time no further change inspecific rotation was noted on continued aeration and irradiation. Thesolvent was stripped off under reduced pressure and the residual methylester of neodiperoxide was recrystallized from aqueous methanol. Thepure methyl 18-hydroperoxy- 6,14-peroxy-A" -dihydroabietietate exhibitedM.P. 147- 147.5 C. with doc. and evolution of gas; +92 (c.=1.0 in 95%ethanol); and peroxide analysis of 1.7 moles peroxide/mole of ester,showing that the product was identical to that prepared in Example 9above in which 18-hydroperoxy-6,14-peroxy A -dihyd-roabietic acid wasesterified with diazomethane.

EXAMPLE 30 A solution of 0.328 g. of vinyl neoabietate ([prepared by theprocedure of J. B. Lewis, W. D. Lloyd, and G. W. Hedrick, J. Org. Chem.,25, 1206 (1960)] reaction of vinyl chloride and the silver salt ofneoabietic acid) and mg. of Eosin YS in 100 ml. of 95% ethanol wascharged to the apparatus described in Example 4 above and was aeratedand irradiated simultaneously for nine hours. The solvent was removed byvacuum stripping and the residual vinyl 18-hydroperoxy-6,l4-peroxy-Adihydroabietate was recrystallized from aqueous methanol. The estercontained 1.6 moles peroxide/mole of ester, [a] +8.6 (c.=1.0 in 95%ethanol), contained no characteristic absorption in the 220-320 my.region, contained infrared absorption bands at 2.8 (-OH), 3.4a, 6.05 and113a (terminal methylene) was soluble in ethanol, methanol, and acetone;insoluble in water and pet. ether.

EXAMPLE 31 A solution of 0.414 g. of n-octyl neoabietate (prepared fromn-octyl bromide and the silver salt of neoabietic acid) and 5 mg. oferythrosin B in 100 ml. of 95% ethanol was charged to the reactordescribed in Example 4 above and aerated and irradiated simultaneouslyfor 5 hours. The alcohol was removed under reduced pressure and theresidual n-octyl 18-hydroperoxy-6,14-peroxy-A -dihydroabietate wasrecrystallized from ethyl alcohol. The product contained 1.7 molesperoxide/ mole of ester; exhibited no characteristic absorption from220- 320 mp; +69 (c.=1.0 in 95% ethanol); exhibited strong infraredabsorption band at 2.88,a.

EXAMPLE 3 2 About 0.5% by weight of each of the following compounds wasdissolved in ml. of freshly distilled styrene contained in a test tube,and the tubes were swept with nitrogen, capped with polyethylenestoppers, and were placed in an oven at 100 together with several tubescontaining no added initiator, but otherwise treated similarly:6,14-peroxy-" -dihydroabietic acid, 18 hydroperoxy-6,14-peroxy-A'-dihydroabietic acid, 7,13-peroxy- A -dihydroabietic acid,18-hydroxy-6,14-peroxy-A -dihydroabietic acid,18-hydroperoxy-6-keto-14-hydroxy- A -dihydroabietic acid, crudephotosensitized oxidized WW gum rosin, and crude photosensitized pinegum. After 4 hr., the blanks were fluid while all of the other solutionswere very viscous. After 40 hours, the blanks consist of soft, fluidgels while the tubes containing the above named materials were hard,glass-like, clear, tough polymeric castings.

The experiment described above was repeated employing acrylic acidinstead of styrene as the monomer. After minutes the first trace ofpolymer appeared in the blanks. All of the solutions containing theadded initiator were hard, clear, tough, polymeric castings at thispoint.

The experiment described above was repeated employing methylmethacrylate as the vinyl monomer in place of styrene. After 2 hr. thefirst trace of polymer appeared in the blanks, an excess of methanol wasthen added to the blanks, which were still fluid, and to the runscontaining the added initiator, which were viscous and syrupy. A heavyprecipitate of insoluble polymer was obtained in all the tubescontaining added initiator and only a trace of polymer in the blanks.

EXAMPLE 3 3 To 15 ml. quantities of a polyester formulation made from afumaric acid, ethylene glycol, phthalic anhydride polyester dissolved inan equal weight of styrene was added 0.5% by Weight of the resin acidderived peroxy compounds listed in Example 32 above. In addition, to asolution of 1/1 styrene polyester containing 0.5% of18-hydroperoxy-6,14-peroxy-A -di-hydroabietic acid was added an equalWeight of cobalt nuodex accelerator. The solutions were placed in testtubes, stoppered, and heated in a hot air oven at C. Several tubescontaining no added peroxy compounds were also included to serve asblanks. After three hours, the blanks were soft, pourable gels while thesolutions containing the added peroxy compounds were all hard, clear,glass-like castings. The toughest casting appeared to be the onecontaining the neodiperoxide plus the cobalt accelerator.

A solution of the polyester resin in styrene described above containing3.0% by weight of 18-hydroperoxy-6,14- peroxy-A' -dihydroabietic acid(neodiperoxide or neoabietic acid diperoxide) and 3.0% by weight ofcobalt Nuodex accelerator was allowed to stand at room temperature fortwo days. A hard, clear, glass-like casting was obtained. A tube of thesame resin containing no added catalysts was still fluid at the end ofthis time.

We claim:

A polymerizable composition consisting essentially of equal parts byweight of an unsaturated polyester resin and monomeric styrene, and acatalytically effective amount of 18-hydroperoxy-6,14-peroxy-A'-dihydroabietic acid.

References Cited by the Examiner UNITED STATES PATENTS 2,775,578 12/1956Fisher et a1 26084.1 2,843,556 7/1958 Moorman 260-863 2,996,515 8/1961Moore et al. 26099 MURRAY TILLMAN, Primary Examiner.

M. FOELAK, Assistant Examiner.

